This invention relates to the use of alkylurethanes of fructans as surfactants, to compositions comprising alkylurethanes of fructans as surfactants, to novel alkylurethanes of fructans and to a process for their manufacture.
Surface-active agents are widely used in compositions for household and industrial applications in which they act as detergents, foaming agents, foam stabilisers, wetting agents, emulsifiers and/or emulsion stabilisers. The oldest type of surface-active agents, mainly used as detergents, are the alkali soaps of fatty acids. Later on these soaps have been replaced to a large extent by much stronger synthetic surfactants. The elder generation of synthetic surfactants consisted mainly of alkylbenzenesulfonates (ABS). However, ABS caused considerable water pollution due to their poor biodegradability. At present, ABS have been largely replaced by linear alkylsulfonates (LAS) having ten or more carbon atoms in the alkyl chain, which present improved biodegradability compared to ABS surfactants.
To day, the search for alternative, more efficient and better biodegradable surfactants is still going on.
According to one approach, sugars such as glucose and sucrose (saccharose) have been used as starting material for the synthesis of non-ionic derivatives with surface-active properties.
V. Maunier et al. (Carbohydrate Research, 299, 49-57, (1997)) disclosed tensio-active properties of several 6-aminocarbonyl derivatives of methyl xcex1-D-glucopyranoside and D-glucose and compared them with the ones of the urethane named methyl 6-O-(N-heptylcarbamoyl)-xcex1-D-glucopyranoside.
T. Lesiak et al. (J. prakt. Chem., 322 (6), 877-883, (1980)) disclosed the use of 1-methyl-2,4-bis(isocyanato)benzene (commonly named tolylene-2,4-diisocyanate; in short 2,4-TDI) for the synthesis of urethanes of glucose and sucrose. First 2,4-TDI was reacted with various aliphatic long chain alcohols or terpene alcohols in a molar ratio 1:1. The reaction essentially occurred with the isocyanate group at position 4 and the urethane-mono-isocyanates obtained were then reacted with glucose, respectively sucrose, to yield the corresponding di-urethanes which presented moderate tensio-activity.
The synthesis of several sucrose N-n-alkylurethanes and their tensio-active properties have been disclosed inter alia by H. Bertsch et al. (J. prakt.
Chem., 11, 108 (1960)) and by W. Gerhardt (Abh. Dtsch. Akad. Wiss. Berlin, Kl. Chem., Geol. Biol., Vol 1966 (6), 24-32, (1967)). These derivatives present moderate to good tensio-active properties but only at rather high concentration. The urethanes have been prepared by reaction of sucrose with the selected n-alkylisocyanate (H. Bertsch et al. o.c.) and by transformation of sucrose with potassium cyanate and an n-alkyl-halogenide in dimethyl formamide (W. Gerhardt, o.c. ). However, sucrose n-alkylurethanes with longer alkyl chains, suffer from a moderate to poor solubility in water.
To improve the solubility in water of sugar n-alkylurethanes, corresponding n-alkylurethanes have been prepared from ethoxylated or propoxylated sugars. The synthesis and tensio-active properties of n-alkylurethanes derived from ethoxylated and propoxylated sucrose, respectively mannitol, have been disclosed by W. Gerhardt (o.c. and German Patent DE 1 518 696). Furthermore, 1-(n-alkyloxy)-ethylurethanes of sucrose have been synthesised and their tensio-active properties determined by T. Lesiak et al. (J. prakt. Chem., 319 (5), 727-731, (1977)).
Moreover, the preparation of miscellaneous urethanes derived from various carbohydrates have been disclosed.
European patent application EP 0 801 077 discloses n-alkyl C1-C18-urethanes of polysaccharides and ethoxylated polysaccharides, in particular of cellulose, and their use as thermoplastic material. Similarly, German patent application DE 43 38 152 A1 discloses n-alkylurethanes of starch and starch derivatives, such as acetylated starch, and their use as thermoplastic material.
European patent application EP 0 157 365 discloses various urethane derivatives of polysaccharides, inter alia inulin tri(phenylcarbamate), and discloses their use in the optical resolution of racemic mixtures.
I. Wolff et al. (J. Am. Chem. Soc., 76, 757 (1954)) disclosed to have prepared urethanes of starch, but later studies by E. Asveld et al. (Carbohydrate Polymers, 4, 103-110, (1984)) revealed that in the aqueous reaction conditions used by I. Wolff et al. no urethanes but only mixtures of the carbohydrate and the urea compounds have been obtained.
In view of the steadily increasing demand for surface-active agents for use in various applications, industry is continuously confronted with the need for alternative surface-active agents, which preferably present improved tensio-active properties and/or biodegradability.
It is the object of the present invention to provide a solution to one or more of the above mentioned problems by the provision of alternative surface-active products which are readily soluble at low concentration in water at room temperature and which present good tensio-active properties and good biodegradability.
In their search for alternative and/or improved surfactants, the inventors have found that certain urethanes of fructans provide a solution to one or more of said problems.
In accordance with these findings, the present invention provides the use of certain alkylurethanes of fructans as surfactants, certain novel alkylurethanes of fructans suitable for use as surfactants, methods for preparing these compounds, and compositions comprising one or more of said alkylurethanes as surfactants and/or stabilisers.
By surface-active agent, surfactant or tensio-active agent are meant herein compounds that reduce the surface tension when dissolved in water or in an aqueous medium, or which reduce interfacial tension between two liquids, between a liquid and a solid or between a liquid and a gas. These terms are used herein interchangeably. The same applies to the terms designating said properties.
By the term alkylurethanes are commonly indicated a class of compounds resulting from the reaction of an alkylisocyanate with an alcoholic hydroxyl group bearing substrate, whereas the individual reaction products are named as N-alkylcarbamates, i.e. as esters of N-alkylcarbamic acid. However, the terms are often, also in this description, interchanged.
Fructans are well known naturally occurring polysaccharides embracing the carbohydrates levan and inulin.
Levans are D-fructans generally consisting of chains of polyfructose of which the fructose units are connected to each other mostly or exclusively by xcex2(2-6) fructosyl-fructose linkages. Levans occur in nature in certain plant species (in this case they are also called phleins) and also originate from the activity of certain bacteria. Levans can be produced, according to conventional techniques, by extraction from certain plants, by fermentation techniques and by enzymatic in vitro synthesis. Levans usually occur as a polydisperse mixture of said polyfructose chains. The chains may be linear, but mostly they are branched.
Inulins are D-fructans too, generally consisting of chains of polyfructose but of which the fructose units are connected to each other mostly or exclusively by xcex2(2-1) linkages. Inulin occurs in nature, in general, as a polydisperse mixture of polyfructose chains most of which are ending in one glucosyl unit. Inulin can be from bacterial origin, from vegetal origin or can be made in vitro by enzymatic synthesis starting from sucrose. Inulin produced by bacteria is more branched than inulin from plant origin and has commonly a higher molecular weight (ranging from about 2,000 up to about 20,000,000), whereas inulin from plant origin is generally composed of linear or slightly branched polyfructose chains or mixtures thereof with a molecular weight commonly ranging from about 600 to about 20,000.
Inulin can be represented, depending from the terminal carbohydrate unit, by the general formulae GFn or Fn, wherein G represents a glucosyl unit, F a fructosyl unit, and n is an integer representing the number of fructosyl units linked to each other in the carbohydrate chain. The number of saccharide units (fructose and glucose units) in one inulin molecule, i.e. the values n+1 and n in the respective formulae above, are referred to as the degree of polymerisation, represented by (DP). Often, the parameter (number) average degree of polymerisation, represented by ({overscore (DP)}), is used too, which is the value corresponding to the total number of saccharide units (G and F units) in a given inulin composition divided by the total number of inulin molecules present in said inulin composition, without taking into account the possibly present monosaccharides glucose (G) and fructose (F), and the disaccharide sucrose (GF). The average degree of polymerisation ({overscore (DP)}) can be determined, for example, by the method described by L. De Leenheer (Starch, 46 (5), 193-196, (1994), and Carbohydrates as Organic Raw Materials, Vol. III, p. 67-92, (1996)).
At industrial scale, inulin is commonly prepared from plant sources, mainly from roots of Chicory (Cichorium intybus) and from tubers of Jerusalem artichoke (Helianthus tuberosus), in which inulin can be present in concentrations of about 10 to 20% w/w on fresh plant material. Inulin from plant origin is, in general, a polydisperse mixture of linear and slightly branched polysaccharide chains with a degree of polymerisation (DP) ranging from 2 to about 100. In accordance with known techniques, inulin can be readily extracted from said plant parts, purified and optionally fractionated to remove impurities, mono- and disaccharides and undesired oligosaccharides, in order to provide various grades of inulin, as e.g. described in European patent applications EP 0 769 026 and EP 0 670 850.
Inulin is commercially available, typically with a ({overscore (DP)}) ranging from about 6 to about 40. Inulin from chicory is for example available as RAFTILINE(copyright) from ORAFTI, (Tienen, Belgium) in various grades. Typical RAFTILINE(copyright) grades include RAFTILINE(copyright) ST (with a ({overscore (DP)}) of about 10 and containing in total up to about 8% by weight glucose, fructose and sucrose), RAFTILINE(copyright) LS (with a ({overscore (DP)}) of about 10 but containing in total less than 1% by weight glucose, fructose and sucrose), and RAFTILINE(copyright) HP (with a ({overscore (DP)}) of at least 23, commonly with a ({overscore (DP)}) of about 25, and virtually free of glucose, fructose and sucrose).
Inulins with a lower degree of polymerisation, usually defined as a (DP)  less than 10, are commonly named inulo-oligosaccharides, fructo-oligosaccharides or oligofructose. Oligofructose can be conventionally obtained by partial (preferably enzymatic) hydrolysis of inulin and can also be obtained by enzymatic in vitro synthesis from sucrose according to techniques which are well-known in the art. Several grades of oligofructose are commercially available, for example as RAFTILOSE(copyright) from ORAFTI, (Tienen, Belgium), e.g. RAFTILOSE(copyright) P95 with a mean content of about 95% by weight of oligofructose with a degree of polymerisation (DP) ranging from 2 to 7 and containing about 5% by weight in total of glucose, fructose and sucrose.
In one aspect, the present invention relates to the use as surface-active agent of a fructan alkylurethane (I), also named fructan N-alkylcarbamate (I), which is composed of saccharide units of general formula (II)
A(Oxe2x80x94COxe2x80x94NHxe2x80x94R)sxe2x80x83xe2x80x83(II)
wherein
A represents a fructosyl unit (F) or a terminal glucosyl unit (G) of said fructan, being a levan or an inulin, with a degree of polymerization (DP) of minimum 3,
(Oxe2x80x94COxe2x80x94NHxe2x80x94R) represents an N-alkylaminocarbonyloxy group, also called an alkylcarbamate group, replacing a hydroxyl group of the saccharide unit A, wherein R represents a linear or branched, saturated or unsaturated alkyl group containing from 3 to 22 carbon atoms and any mixture thereof, and s represents the number of alkylcarbamate groups per saccharide unit which is expressed as degree of substitution (commonly abbreviated as DS), i.e. the average number of substituents per saccharide unit of said fructan, and which DS has a value ranging from about 0.10 to about 2.0.
The number of hydroxyl groups per saccharide unit of the fructan molecules which can be substituted by a carbamate group is for a non-terminal, non-branched saccharide unit maximal 3, whereas said number for a terminal saccharide unit and for a non-terminal branched unit is, respectively, 4 and 2. Furthermore, since the DS represents an average number of substituents per saccharide unit, it is obvious that in a fructan N-alkylcarbamate (I) molecule there may be saccharide units present which are not substituted by an alkylcarbamate group at all.
In another aspect, the present invention relates to a composition comprising as surface-active agent one or more fructan alkylurethanes (I) defined above.
In a further aspect, the present invention relates to novel fructan alkylurethanes (I) defined above.
In still a further aspect, the present invention relates to a process for the manufacture of fructan alkylurethanes (I) defined above.
In still another aspect, the present invention relates to a process for the manufacture of compositions comprising as surface active agent one or more fructan alkylurethanes (I) defined above.
In a preferred embodiment of the present invention, the fructan alkylcarbamate (I) is made from a levan. In an other preferred embodiment, the fructan alkylcarbamate (I) is made from an inulin. Levans and inulins which are suitable according to the present invention include, respectively, polydisperse levans and inulins composed of essentially linear polysaccharide chains, of essentially branched polysaccharide chains, as well as of respective mixtures thereof.
In view of its better biodegradability, the inulin is preferably a polydisperse linear inulin or a polydisperse slightly branched inulin or a mixture thereof. When the inulin is a slightly branched one, it is preferably an inulin of which maximally about 3% of the fructose units of the inulin chains present 3 fructosyl-fructose bonds. The degree of branching can be determined by known methods, for example by permethylation techniques in combination with gas chromatography analysis, e.g. as described by L. De Leenheer et al. in Starch, 46(5), 193-196 (1994).
In a more preferred embodiment, said polydisperse inulin consists of polysaccharide chains with a degree of polymerisation (DP) ranging from 3 to 100, typically from about 5 to about 75. Even more preferably said polydisperse inulin has an average degree of polymerisation ({overscore (DP)}) between 6 and 40, most preferably a ({overscore (DP)}) ranging from about 10 to about 35.
The alkyl group of the alkylurethanes (I) of the present invention, i.e. the R group in formula (II), is preferably a saturated alkyl group, more preferably a saturated C3-C18 alkyl group, and most preferably a saturated linear or slightly branched C6-C18 alkyl group or a mixture thereof. Typically alkyl groups include propyl, butyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl and octadecyl, and any mixtures thereof.
In another preferred embodiment, the alkyl group is a mono-unsaturated C3-C18 alkyl group, more preferably a mono-unsaturated C6-C18 alkyl group, even more preferably a mono-unsaturated C6-C16 alkyl group. Typically suitable mono-unsaturated alkyl groups, i.e. alkenyl groups, include hexenyl, octenyl, decenyl, dodecenyl, tetradecenyl, hexadecenyl, octadecenyl, and any mixtures thereof.
In a further embodiment, the alkyl group R can represent a mixture of one or more saturated alkyl groups with one or more unsaturated, preferably mono-unsaturated, alkyl groups.
The alkylurethanes (I) in accordance with the present invention, particularly the ones derived from inulin, have a degree of substitution (DS) preferably ranging from about 0.15 to about 1.5, more preferably from about 0.20 to about 1.2, even more preferably from about 0.4 to about 0.8, and most preferably from about 0.50 to about 0.60.
The positions on the saccharide units of the fructan alkylurethanes (I) where the said alkylcarbamate substituent or substituents are located, are not critical with respect to the present invention.
The fructan alkylurethanes (I) can be prepared in analogy with conventional methods for the preparation of urethanes of mono- and disaccharides, and of urethanes of polysaccharides such as starch. The products (I) can be prepared, for example, by reacting the substrate carbohydrate (levan or inulin) with the selected alkylisocyanate, in solution in a solvent which is inert with respect to the polysaccharide, the isocyanate and the reaction product. Suitable solvents include, for example, rather polar solvents or solvent mixtures, free of reactive hydroxyl and amine groups, such as dimethyl formamide and dimethyl sulfoxide.
Saturated alkylisocyanates can be prepared conventionally, e.g. by reacting a primary or secondary alkyl-amine with phosgene. Unsaturated alkylisocyanates can be prepared similarly from alkenyl-amines. Alpha-beta unsaturated alkylisocyanates of formula R2R3 Cxe2x95x90CHxe2x80x94NCO (III) wherein R2 represents hydrogen or an alkyl group and R3 represents an alkyl or vinyl group, can be prepared by condensation of the aldehyde R2R3 C Hxe2x80x94CHO with Me3 Cxe2x80x94NH2, followed by reaction of the resultant Schiff base (in equilibrium with its enamine form) with phosgene, and thermal elimination of Me3 Cxe2x80x94Cl, as disclosed by K. Koenig et al. (Angew. Chem., 91(4), 334-335 (1979)). Furthermore, various unsaturated alkylisocyanates are disclosed, inter alia in U.S. Pat. No. 3,890,383 and U.S. Pat. No. 3,803,062 of Dow Chemical Co.
The reaction between the fructan and the alkylisocyanate can be carried out, preferably in the absence of humidity, over a wide temperature range, typically from room temperature till the reflux temperature of the reaction mixture, preferably at a temperature from about 60xc2x0 C. to about 80xc2x0 C. The fructan is dissolved in a suitable solvent, where necessary under heating, and the isocyanate (optionally dissolved in the same or in another inert solvent which is preferably miscible with the former solvent) is then added to the dissolved fructan slowly and under stirring. The desired degree of substitution of the fructan alkylurethanes (I) can be obtained by controlling the ratio of the reactants. Since the reaction of an alkylisocyanate with an alcoholic hydroxyl group to form an urethane is virtually quantitative, the degree of substitution of the compounds (I) can be controlled by selection of the proper mole ratio of the alkylisocyanate per saccharide unit of the fructan substrate. Usually the reaction mixture is heated during a certain time with stirring in order to complete the reaction between the reagents. The reaction mixture can be worked up, for example, by precipitating the formed fructan alkylurethane (I) by pouring the reaction mixture in a precipitant solvent, i.e. a solvent which is miscible with the solvent or solvents used to dissolve the reagents but in which the fructan alkylurethane (I) is virtually not or poorly soluble.
A convenient method to synthesise a desired sucrose alkylurethane which is also suitable for the synthesis of fructan alkylurethanes (I) according to the present invention, has been described by W. Gerhardt, Abh. Dtsch. Akad. Wiss. Berlin, KL. Chem. Geol. Biol., Vol 1966(6), 24-36, (1967) (C.A., 68, 14323). It involves the transformation, in a one pot reaction, of sucrose with potassium cyanate and an alkyl halogenide, preferably an alkyl bromide, in dimethyl formamide.
Furthermore, the inventors have developed an alternative, very suitable method for the manufacture of fructan alkylurethanes (I), which enables to use as substrate, a fructan which may contain mono- and disaccharides to an extent of up to about 10% by weight. According to this process, the starting fructan, for example inulin containing about 8% mono- and disaccharides (such as e.g. RAFTILINE(copyright) ST from ORAFTI(copyright), Belgium) or oligofructose containing about 5% mono- and disaccharides (such as e.g. RAFTILOSE(copyright) P95 from ORAFTI(copyright), Belgium), are reacted in an inert solvent or solvent mixture (termed herein first solvent) with the alkylisocyanate which is optionally dissolved in the same or in another inert first solvent. After the reaction is completed, usually by heating under stirring for some time, the reaction mixture is treated, preferably after concentration by evaporation of a part of the first solvent under reduced pressure, with a solvent or solvent mixture (termed herein precipitant solvent) wherein the first solvent of the reaction as well as the alkylurethanes of the mono- and disaccharides remain in solution, but wherein the fructan alkylurethanes (I) are virtually not soluble. Accordingly, the formed fructan alkylurethanes (I) precipitate in the precipitant solvent from which they can be isolated easily by a conventional physical separation technique such as decantation and/or filtration, or centrifugation. To complete the removal of remaining first solvent and possibly present small amounts of alkylurethanes of mono- and disaccharides, the isolated reaction product can be washed and/or triturated with the precipitant solvent or with another suitable precipitant solvent, or other conventional techniques can be used such as e.g. redissolving and reprecipitation of the reaction product, followed by its isolation and drying.
Suitable first solvents include, for example, dimethyl formamide and dimethyl sulfoxide; suitable precipitant solvents include, for example, ethers, ketones, alcohols and esters.
The fructan alkylurethanes (I) are readily soluble at low concentration in water at room temperature and they present good to excellent tensio-active properties, even at very low concentration. Accordingly, they are very useful as surface-active agents because they significantly reduce interfacial tension between an aqueous liquid and a non-aqueous liquid, between an aqueous liquid and a solid, and between an aqueous liquid and a gas.
Preferably the fructan alkylurethanes (I) are used as surface-active agent in an aqueous medium, more preferably in water, at a concentration ranging from about 0.0005% to about 5%, preferably from about 0.001% to about 3%, more preferably from about 0.005% to about 2%, even more preferably from about 0.01% to about 1% (concentration in % weight/volume {% w/v}).
As a non-limiting illustration of the present invention, the preparation and tensio-active properties of some fructan alkylurethanes (I) are shown in the Examples and Tables below.
The reaction is preferably carried out in the absence of humidity with anhydrous reagents and solvents. The fructan, preferably conventionally dried, e.g. under vacuum over P2O5 or by azeotropically distilling off of the water by means of a suitable solvent, is dissolved, with stirring under heating, in a minimum amount of solvent, e.g. dimethyl formamide (DMF). To avoid thermal degradation, the temperature has to be kept below about 110xc2x0 C. Preferably the mixture is kept between about 60xc2x0 C. to about 80xc2x0 C. until all fructan has dissolved. Then, at a temperature between about 60xc2x0 C. to about 80xc2x0 C., a pre-defined amount (determined in mole equivalents on fructose units in the fructan; for the calculation, the amount of fructan starting material is taken as composed of 100% fructose units) of a selected alkylisocyanate, optionally diluted with a suitable solvent, e.g. DMF, is added slowly, preferably dropwise, under vigorous stirring to the fructan solution and the obtained mixture is stirred at said temperature for a certain time to complete the reaction. After a few hours, the mixture may already turn cloudy by precipitation of formed fructan alkylurethane (I), but usually stirring is continued for about 24 hours in total after addition of the alkyl-isocyanate. Accordingly, the mixture is cooled to room temperature, optionally part of the solvent is removed by evaporation under reduced pressure, and a precipitant solvent, e.g. diethyl ether, is added under stirring. The formed fructan alkylurethane (I) precipitates, usually as a more or less sticky mass. After removal of the supernatant solvent, the sticky mass is repeatedly treated under stirring with solvent mixtures with decreasing polarity until the fructan alkylurethane (I) is obtained in powder or granulate form, which is then isolated and dried.
Alternatively, in order to avoid the formation of said sticky mass, the formed fructan alkylurethanes (I) can advantageously be isolated after completion of the reaction by slow, preferably dropwise, addition under vigorous stirring of the cooled and optionally concentrated reaction mixture to an excess of precipitant solvent, e.g. ether. Typically the formed fructan alkylurethanes (I) precipitate in a granular or powder form and can be easily isolated. After their separation from the solvent mixture, e.g. by filtration, the fructan alkylurethanes (I) can be further purified by washing, trituration with a non-solvent, e.g. ether, or they may be redissolved and reprecipitated to remove possibly included solvent and impurities.
The formation of the fructan alkylurethanes (I) has been confirmed by IR- spectroscopy {presence of xe2x80x94NHxe2x80x94COxe2x80x94 band at 1705 cmxe2x88x921 (amide I band) and 1543 cmxe2x88x921 (amide II band)} and by 13C-NMR spectroscopy (where following resonance peaks were found for inulin N-n-octylcarbamate: ∂{ppm; 68 MHz}: 13.87; 22.05; 26.23; 28.64; 29.33; 30.74; 31.21; 35.77; 61.45; 73.99; 76.56; 81.59; 103.19 and 156.08).
As to the synthesis of inulin alkylcarbamates (I), the yields commonly obtained are good. For the synthesis made at a 0.2 mole scale, typical yields of inulin octylcarbamates (DS: 0.52-0.59) obtained are as follows:
with RAFTILINE(copyright) HP (inulin with ({overscore (DP)}) of about 25): yield about 70-95%
with RAFTILINE(copyright) ST (inulin with ({overscore (DP)}) of about 10): yield about 55-75%
with RAFTILOSE(copyright) P95 (95% w/w oligofructose with ({overscore (DP)}) from 2 to 7):
yield about 50-65%.
The above general procedure is further illustrated by the following examples. The tensio-active properties of the fructan alkylurethanes (I) were determined by measuring the surface tension at 20xc2x0 C. of an aqueous solution of the compounds with a tensiometer following the Wilhelmy or the Du Nouy Ring method.
In a 100 ml flask, 5.0 g inulin (RAFTILINE(copyright) HP with a ({overscore (DP)}) of about 25; 27.7 millimole fructose equivalents) were dissolved under stirring at about 70xc2x0 C. in 8 ml dry DMF. To the yellowish solution 2.9 ml n-octylisocyanate (16.7 millimole; 0.6 mole equivalents determined on fructose units) were added dropwise with stirring at 70xc2x0 C. Stirring was continued for 24 hours at 70xc2x0 C. Then, after cooling, most of the DMF was evaporated under reduced pressure (xc2x16.7 Pa; 0.05 mm Hg). To the residue at room temperature, 10 ml of dry diethyl ether was added under stirring and the mixture was stirred for 1 hour. The white precipitate formed was isolated by filtration, washed with 15 ml dry ether and the residual solvents (DMF and ether) were removed under reduced pressure (xc2x16.7 Pa; 0.05 mm Hg), yielding inulin N-n-octyl-carbamate (1) with a degree of substitution (DS) of 0.56 (determined by 1H-NMRxe2x80x94270 MHz). Compound (1) was obtained as a white powder in a yield of 92%. The efficiency calculated as [DS/(molar ratio octylisocyanate/fructose equivalent)] was 93%. The surface tension of product (1) in a 0.01% w/v solution in water was 32.4 mN/m.
In a 500 ml flask, 33.3 g inulin (RAFTILINE(copyright) HP with a ({overscore (DP)}) of about 25; 0.185 mole fructose equivalents) was dissolved at 60xc2x0 C. in 60 ml dry DMF. To the yellowish solution kept at 60xc2x0 C., 19.56 ml n-octylisocyanate (0.111 mole; 0.6 equivalents determined on fructose units) was added dropwise under stirring. Then the mixture was heated to 70xc2x0 C. and stirred for 24 hours. After cooling to room temperature, 150 ml diethyl ether was added slowly under vigorous stirring. After stopping the stirring, the reaction product quickly settled and most of the solvent was removed by decantation. Under stirring 100 ml dry ether was added to the residue, which became gummy-like. After addition of another 50 ml ether the residue started to granulate and after 1 hour stirring a white suspension was formed. The precipitated solid was filtered off, washed with dry ether and dried under reduced pressure (xc2x16.7 Pa; 0.05 mm Hg), yielding inulin N-n-octylcarbamate (2) with a degree of substitution (DS) of 0.58 (determined by 1H-NMRxe2x80x94270 MHz) in a yield of about 95% and with an efficiency of 96%. The surface tension of product (2) in a 0.01% w/v solution in water was 34 mN/m.
Several other inulin alkylurethanes (I) have been prepared by reacting various grades of inulin with various n-alkylisocyanates in accordance with the general procedure described above, and their tensio-active properties were determined. These products and data, including also Examples 1 and 2 above, are listed in Table 1 below.
Furthermore, for some of the inulin N-n-octylcarbamates (I), the critical micelle concentration (CMC) has been determined which are shown in FIG. 1, FIG. 2 and FIG. 3.
FIG. 1: presents the surface tension in function of the concentration of inulin ({overscore (DP)}: 25) N-n-octylcarbamate (DS: 0.56) (18) measured at room temperature in water and the resulting critical micelle concentration (CMC=12.8 10xe2x88x923 g/l);
FIG. 2: presents the surface tension in function of the concentration of inulin ({overscore (DP)}: 10) N-n-octylcarbamate (DS: 0.53) (20) measured at room temperature in water and the resulting critical micelle concentration (CMC=16.0 10xe2x88x923 g/l);
FIG. 3: presents the surface tension in function of the concentration of inulin (95% DP: 2-7) N-n-octylcarbamate (DS: 0.51) (21) measured at room temperature in water and the resulting critical micelle concentration (CMC=23.9 10xe2x88x923 g/l).